Many dental and medical devices made from polymers or composites need to bond or adhere to other materials, such as other resins or composites, or to living tissue, such as bone. In dentistry, it has been found that the adhesion of polymerised fiber reinforced composite having a thermosetting polymer matrix made for example of a copolymer of 2,2-bis(4-(2-hydroxy-3-methacryloxy)phenyl)propane (BisGMA) and triethyleneglycoldimethacrylate (TEGDMA) to a new polymeric material is difficult to obtain. Poor adhesion can result in e.g. debonding of parts of the composite, loosening or delamination of a root canal post made from said composite.
The problem has partly been resolved by the invention described in patent application WO 99/45890 (Vallittu et al.) where a thermoplastic membrane was used to cover the thermosetting polymer matrix of the prepreg. The thermoplastic membrane allowed adhesion of the new polymeric material by means of interdiffusion (interpenetrating polymer network).
In other medical applications of fiber-reinforced composites, like in orthopaedic implants (e.g. hip prostheses), there is a need to achieve bonding of bone to the implant. The technique of roughening the surface of the implant has most widely been used to increase the bonding of the metal surface of the implant to the bone, together with the help of acrylic bone cements. Clinical experience has shown that a relatively great number of detachments of endosseus implant prostheses occur after five to ten years use of the prosthesis.
Numerous publications disclose the use of prepregs and composites in medicine. U.S. Pat. No. 4,894,012 discloses passive dental appliances of fiber-reinforced composites being fully impregnated with composite. U.S. Pat. No. 5,921,778 discloses a hybrid woven material formed of glass yarns and synthetic yarns to prevent fray upon cutting. U.S. Pat. No. 5,919,044 discloses a flexible post in a dental post and core system. U.S. Pat. No. 5,816,816 discloses a method of producing a dental post for use in restoring or stabilizing one or more teeth. The method includes the steps of creating a hole in a tooth and obtaining a woven hollow rope, which is mounted over a mandrel and inserted into the hole. Patent application DE 29 32 435 discloses a hip joint and a dental implant having fiber structure on a metal core.
U.S. Pat. No. 5,723,007 discloses a biocompatible composite material with a plastic matrix having a felt of collagen fibers contained therein, wherein the collagen fibers project out from the surface of the material so that it can be colonized with human cells prior to implantation. The material is manufactured by impregnating collagen fibers with a matrix, partially curing said matrix and removing the unpolymerized matrix. The fibers that project out from the surface of the material are thus partially covered by said matrix.
GB 2 214 087 discloses a composite canal post wherein the surface is mechanically roughened in order to increase the bonding strength of the surface. In U.S. Pat. No. 5,839,900 a dental prosthesis is proposed in which the surface is treated by abrasion or erosion to expose the fibers.
U.S. Pat. No. 5,676,546 discloses partial and full prosthetic denture plates and processes to make them. A partial denture plate comprised of a denture base formed of a composite laminate having an intermediate layer of a woven fabric with non-woven veils disposed on opposite sides thereof is encapsulated in a polymeric resin. The denture base is moulded to conform to a shape of a patient's mouth. The denture base has at least one tab extending from the denture base. The tab is oriented to be in alignment with the patient's natural teeth. A synthetic tooth is moulded on each tab resulting in a denture device having a fiber-reinforced composite base and a synthetic tooth, or teeth, moulded on each tab, the tab or tabs made of and extending from the fiber-reinforced composite. Similarly, a full denture plate is disclosed. A rib is positioned on a parabolic strip of the composite laminate, the rib generally conforming to a patient's gum line. Artificial teeth are then moulded on the rib resulting in a full, prosthetic, denture plate.
U.S. Pat. No. 3,906,550 discloses a prosthetic devices for replacement, attachment and reconstruction of bone structure in skeletal systems of humans and animals. The prosthetic devices may be a fiber-metal structure of sufficient section to support loads adequately or may include a solid load-carrying member having a fiber-metal structure secured to the surface thereof. The fiber-metal structure is sintered and open-pored so that the bone and tissue into which the prosthetic device is implanted will grow into such fiber metal structure.
DE 41 33 690 discloses ready-made dental crowns and mastication surfaces, the occlusal halves of one or more crowns are moulded in the form of a plastic covering to existing metallic dental crowns, or to prosthetic constructions, and are applied to them by pressing with a finger or an instrument. The crowns have projections and depressions and are hardened after forming by polymerisation or sintering. The crown consists preferably of only a reinforcing layer between 0.5 and 5 mm thick in the shape of the mechanism surface. The plastic material may be pressure-, temperature- or light-hardening composites, or a plastic, or sintered metals or plastic-metal composites. In particular inorganic substances are used, and the material is reinforced with fibers or fabric preferably made of synthetic or natural fibers.
Some prior art documents thus disclose prepregs and composites wherein the reinforcing fibers project out from the surface. The drawbacks of the proposed prepregs and composites are however that either the fibers are at least partially covered by the matrix or the fibers have been revealed using mechanical treatment that partly destroys the fibers and in consequence decreases the mechanical strength of the fibers. The mechanical strength of a product manufactured by using such a prepreg is thus not accurate and specified.